The present invention relates to a structural member superior in water repellency for electric wires, building materials, ships, antennas, air crafts, etc; and a method for manufacturing the same.
Water repellent treatment has been conventionally performed for preventing adhesion of droplets or preventing pollution. Various water repellent materials and water repellent treatments have been developed and used in a variety of products including electronic equipment. For example, in order to obtain an electric wire to which snow hardly adheres, JP-A-3-230420 proposes a method in which a carbon containing thin film is formed on the surface of an aluminum wire or the like, and the film-formed wire is subsequently passed through a space where a fluorine compound is ionized so that a fluorine compound thin film is formed on the wire. However, plasma polymerization of fluorine film is performed in this method. Accordingly, the thin film may be easy to peel off and inferior in adhesion. In addition, JP-A-3-84069, JP-A-4-258675 and JP-A-2-238941 propose paints to be applied to ships, marine building materials, water transport pipes, etc. in order to prevent ice-adhesion or snow-adhesion or to prevent corrosion. However, there is a problem that the paint is easy to peel off because the paint is applied in the form of a coating.
Further, JP-A-6-93121 proposes a method in which a surface of a base material is roughed by using FRP or the like as filler and a chlorosilane surface active agent is absorbed in the roughed surface to perform water-repellent and oil-repellent treatment, in order to obtain a member which is superior in water repellency, oil repellency and antifouling property. In addition, JP-A-4-288349 proposes a technique for obtaining a water-repellent and oil-repellent film in which a surface is roughed by making a surface layer contain particulates or by applying chemical etching to the surface, and a water-repellent polymer layer is chemically bonded with the surface so as to form a film on the surface. However, any technique disclosed in the above publications has a problem that the film is uneven in height of the surface, insufficient in mechanical strength, problematical in durability and scratch resistance, and not uniform in water repellency. In addition, JP-A-10-156282 proposes a technique in which a water-repellent resin film of hydrophobic resin containing particulate powder is formed on a surface of metal material having a 0.1 to 50 xcexcm fine irregularity structure. However, this also has a problem that the film is insufficient in mechanical strength and not uniform in water repellency.
Although those which have a water-repellent function are heretofore proposed as mentioned above, each of the techniques has a problem in durability and scratch resistance, so that the water-repellent function cannot be maintained over a long term.
It is an object of the present invention to provide a structural member in which not only a super water-repellent function but also high durability and high scratch resistance can be obtained; and to provide a method for manufacturing such a structural member.
(1) A structural member according to an aspect of the present invention is configured such that a water-repellent structure which is constituted by appropriate irregularities of protrusion portions and recess portions and which is uniform in height of the protrusion portions is formed on the external surface of the structural member.
(2) A structural member according to the present invention is configured such that in the above-mentioned structural member (1), the depth of each of the recess portions is not less than a predetermined value.
(3) A structural member according to another aspect of the present invention is configured such that in the above-mentioned structural member (1) or (2), the irregularities have a size enough to prevent a droplet from falling into a recess portion and to allow the droplet to come into contact with an air layer in the recess portion.
(4) A structural member according to a further aspect of the present invention is configured such that in any one of the above-mentioned structural members (1) to (3), a water-repellent film reactively bonded with the irregularities of the water-repellent structure is formed on the irregularities.
(5) A structural member according to a further aspect of the present invention is configured such that in any one of the above-mentioned structural members (1) to (3), the water-repellent structure is constituted by irregularities formed on a base material having a water-repellent function.
(6) A structural member according to a further aspect of the present invention is configured such that in any one of the above-mentioned structural members (1) to (5), the irregularities comprises the protrusion portions arranged in distribution in lines or in the form of a lattice.
(7) A wire according to a further aspect of the present invention is configured such that a jacket of the wire is constituted by a structural member according to any one of the structural members (1) to (6).
(8) A building material according to a further aspect of the present invention is configured such that the building material has a surface which is constituted by a structural member according to any one of the structural members (1) to (6).
(9) A ship member according to a further aspect of the present invention is configured such that the ship member has a surface constituted by a structural member according to any one of the structural members (1) to (6).
(10) An antenna according to a further aspect of the present invention is configured such that the antenna has a surface constituted by a structural member according to any one of the structural members (1) to (6).
(11) An air-craft member according to a further aspect of the present invention is configured such that the air-craft member has a surface constituted by a structural member according to any one of the structural members (1) to (6).
(12) A method for manufacturing a structural member according to a further aspect of the present invention is configured such that in a method for manufacturing any one of the structural members (1) to (6), the irregularities of the water-repellent structure are formed by a mold having a shape corresponding to the irregularities.
(13) A method for manufacturing a structural member according to a further aspect of the present invention is configured such that in the manufacturing method (12), a roller having an outer circumferential portion in which the shape corresponding to the irregularities of the water-repellent structure is formed is pressed onto the surface of a base material.
(14) A method for manufacturing a structural member according to a further aspect of the present invention is configured such that in the manufacturing method (12), a not-yet-solidified base material is passed through a die having an inner circumferential portion in which the shape corresponding to the irregularities of the water-repellent structure is formed.
(15) A method for manufacturing a structural member according to a further aspect of the present invention is configured such that in the manufacturing method (14), the water-repellent structure is manufactured by use of a photolithography method and an etching method. This etching method is, for example, a trench dry etching method; an anodic electrolysis method; an anisotropic wet etching method; an isotropic wet etching method; or an isotropic dry etching method.
In the present invention, a water-repellent structure in which irregularities are formed in the outer surface and the protrusion portions of the irregularities are made uniform in height as mentioned above to thereby obtain not only a super water-repellent function but also high durability and high scratch resistance. That is, if the protrusion portions are uneven in height as in the conventional case, portions in which a super water-repellent function cannot be obtained are formed and the portions have an insufficient mechanical strength and easily wear, so that there is a problem in durability and scratch resistance. However, in the present invention, such a problem is solved. In addition, when a water-repellent film is provided, the water-repellent film is reactively bonded with the irregularities of the water-repellent structure, so that the water-repellent film is hardly peeled off. In addition, when the water-repellent structure is manufactured by a photolithography method and an etching method in the present invention, it is possible to make the protrusion portions uniform in height with precision. The details of the present invention including its operation principle will be explained in Embodiment 1 which will be described below. In the present invention, it is defined that the conception of super water-repellency includes super oil-repellency.